Ecological Concepts of Integrated Weed Management

Dr. Jane Mangold

Extension Invasive Plant Specialist

Montana State University

What is ecology?

Relationships between organisms and their environments

Ecosystems (organisms + environments) are complex

Many parts, each of which contributes to the whole in different ways

What ecology is not:

Environmental advocacy

Political activism

Ecologically-based Invasive Plant Management

Understand how an invasive plant population interacts with itself and with desired vegetation

Understand how environment (climate, elevation, aspect, herbivores, humans, etc.) affects these interactions

Manipulate biotic and abiotic factors to influence plant community dynamics

Favor desirable vegetation

Disfavor weeds

Treating Symptoms vs. Causes

Traditional Management

WEED

Biocontrol

Revegetation

Tilling/diskingMowing

Herbicides

Grazing

Fire

Hand-pulling

Fertilization

Prevention

Irrigation

Future Management--EBIPM

Life cycle of weed

Biocontrol

Revegetation

Tilling/disking

Mowing

Herbicides

Grazing

Fire

Hand-pulling

FertilizationPrevention

Irrigation

SuccessionDesired

Vegetation

SuccessionProcess whereby one plant community changes into another. It involves the immigration and extinction of species, coupled with changes in the relative abundance of different plants.

-Plant Ecology by M.J. Crawley Disturbance

Invasion is a form of succession!

Tansy ragwort colonizationNative species colonization

OR

Disturbance

Managing succession

Site Availabilit

y

Species Performance

Species Availability

Plant Community Undesired State

Plant Community Desired State

Tim

e

Managing Plant Communities

Site Availabili

ty

Species Performance

Species Availability

•Disturbance•Size•Severity•Timing•Patchiness•Frequency

•Dispersal•Vectors•Landscape

•Propagule Pool

•Decay rate•Land use

•Resource availability•Soil•Microclimate

•Ecophysiology•Germination•Assimilation•Growth rate

•Life history•Allocation•Reproductive time•Reproductive mode

•Stress•Climate•Prior occupants

•Competitors•Identity•Consumers•Disturbance•Resource base

•Allelopathy•Soil•Microbes•Neighbors

•Consumers•Identity•Cycles•Plant defenses•Patchiness

(Pickett et al. 1987; Sheley et al. 1996; Krueger-Mangold et al. 2006)

Initial Plant Community

Site Availability

Species Performance

Species Availability

Final Plant Community

Grazing

Fire

Drill seed

Broadcast seed

Grazing

Biological control

Hand pulling

Repeated Spring Grazing

Fertilization

Mowing/cutting

Tilling

Hand pulling

Herbicide

Herbicide

Ecological Framework Useful for Management

Aerial seeding

Are

a in

fest

ed

Time

Exclusion

Suppression/Containment

Early detection/ Eradication

Effective control unlikely without

massive resource inputs Restoration may be required!

carrying capacity

Invasion Progression vs. Management Strategy

Cost o

f contro

l

Public awareness

usually begins

Are

a in

fest

ed

Time

Prevention

Containment

Early Detection-Rapid Response (EDRR)

Restoration

carrying capacity

Invasion Progression vs. Management Strategy

Cost o

f contro

l

Management Strategies--Prevention

Education and awareness!!!

Protect weed-free areas

Large majority of U.S. is NOT infested

In MT, 7.6 million acres infested/93 million acres total = 8%

Limit disturbance (site availability) and weed seed dispersal (species availability)

Maintain healthy, competitive vegetation (species performance)

Communication among land managers

Management Strategies—Early detection/rapid response

Mobile, global society

Invasive plants will continue to spread

Catch infestations early when eradication is still possible (limit species availability)

Develop survey and inventory protocol (where are sites and species available?)

Prioritize those areas most susceptible to invasion

Highways

Railways

Trails

Water channels

EDRR in Montana—Dyer’s Woad

Year

1999 2000 2001 2002 2003 2004 2005

Lo

g (

Po

pu

latio

n S

ize

)

2

3

4

5

6

7

8

9

10

Log of the Projected Population SizeLog of the Actual Population Size

(Pokorny and Krueger-Mangold 2007)

Program cost from 1985-2005 = $225,000

Estimated cost of herbicide application in 2005 without program

= $1.9 million

Management Strategies--Containment

Integrated Weed Management

Application of multiple control measures that complement one another (address all 3 causes of plant community dynamics)

Mechanical

Biological

Chemical

Cultural

Containment—Adaptive Management

Management Strategies--Restoration

May be necessary if area has been dominated by invasive plants for a long time

Control weedy species (site availability and species performance)

Introduction of desirable species through revegetation (species availability)

Difficult and unpredictable—but often necessary!

Summary

Treat cause of invasion, not just symptoms

Identify and manage most influential ecological relationships that are leading to invasion and encouraging persistence of invasive plants

Site availability

Species availability

Species performance

Summary

Gear management strategy toward stage of invasion

Prevention

Early detection/Rapid response

Containment

Restoration

Adaptive management

Questions?